Two-stroke internal combustion engine burn a mixture of fuel and oil. Many two-stroke internal combustion engines use a carburetor to supply the mixture of fuel, oil and air to the combustion chambers of the engine. The mixture of fuel, oil and air flows from the carburetor, to the crankcase, then through scavenge ports to the combustion chambers.
Such carbureted engines have some drawbacks. They do not provide for a precise control of the fuel being supplied. They also produce a substantial amount of polluting emissions.
One of the advancements made to two-stroke internal combustion engines consists in replacing the carburetor with a throttle body and a port fuel injector that injects fuel upstream of the combustion chamber. The use of the port fuel injector allows for a more precise control of the fuel quantity being delivered and has helped reduce the amount of polluting emissions being produced.
In recent years, the port fuel injectors have been replaced in some two-stroke engines by direct fuel injectors such as the E-TEC™ fuel injector from BRP™. The direct fuel injectors inject fuel directly into the combustion chambers of the engine. As a result of the use of the direct fuel injectors, the engine performance has improved, even more precise control of the fuel quantity being injected is possible, less oil is used, and the amount of polluting emissions, such as carbon monoxide, has been reduced even more.
Although direct fuel injection has helped improved two-stroke engines, as the demand for even higher performance engines continues, the use direct fuel injectors has some drawbacks. For example, at very high engine speed (RPM), there is a very short period of time during which fuel can be injected and then mix with the air in the combustion chamber. As such, the fuel may not have the time to properly atomized, resulting in larger droplets of fuel being combusted, which emits more soot than when the fuel has properly atomized.
Although some of the above drawbacks could be resolved by switching to a four-stroke engine, doing so would result in losing the advantages typically associated with two-stroke engine, namely a simplified construction, more power (two-stroke engines have an explosion in each combustion chamber at every revolution, four-stoke engines at every two revolutions), and a lighter weight. These advantages of two-stroke engines are important features for vehicles such as motorcycles, snowmobiles and other recreational vehicles.
There is therefore a desire for a two-stroke engine having the advantages associated with direct fuel injection while addressing at least some of its drawbacks.